There are numerous forms of adjustable shock absorbers which have a reservoir surrounding a hydraulic cylinder to receive the oil pumped out of the cylinder as a piston in the cylinder is forced into the cylinder by a force such as that generated by a shock, etc. At that time the oil is pumped from the cylinder through a plurality of passages, a plurality being used to increase the resistance to the applied force as the piston moves deeper into the cylinder by reason of the piston blocking one or more. An adjustable control valve is used in conjunction with each of the passages to permit the force resistance of the shock absorber to be varied as desired. The present invention is concerned with an improved form of that control valve.
A common form of the prior art control valves has been a sleeve which fits about a hydraulic cylinder and is movable with respect to the cylinder so as to vary the size of the passages leading from the ports in the cylinder to the hydraulic fluid reservoir. In some instances the sleeve is moved axially so as to vary the alignment of openings in the sleeve with respect to the ports in the cylinder and thereby change the cross-sectional size of the passage at that point. Examples of such a structure will be seen in U.S. Pat. Nos. 3,693,767 and 3,998,302. In other instances the sleeve is movable rotationally so as to vary the effective cross-sectional size of a part of the passageway. See, for example, U.S. Pat. Nos. 3,997,037 and 3,478,846. Other forms have included a rotatable valve member fitting within the piston (U.S. Pat. No. 3,491,993); a separate sleeve valve or the like received within a chamber contiguous to the cylinder, with the sleeve being rotatable to adjust the passage size (U.S. Pat. No. 3,446,317); and a rotationally adjustable valve in the end of the cylinder (U.S. Pat. No. 2,627,405 and 3,990,548).
The principal object of the present invention is to provide a form of valve for such a hydraulic shock absorber which will have a high degree of accuracy in the setting of the valve and which will be little affected by changes in viscosity; and such a valve which will be easy to service should maintenance be required. The present invention accomplishes this by the use of a separate spool valve mounted in the hydraulic fluid reservoir and having a spool which, when rotated, is moved axially by threads which interengage the spool and the valve body. These threads are at one end of the spool and at the other end the spool has a gear which is engaged by a gear on an operating shaft rotatable about an axis radially aligned to the axis of the spool. One end of the valve is accessible through the opening within which the operating shaft is mounted while the other end of the valve is accessible through ports in the shock absorber body. The spool has lands thereon which move across the inner ends of openings in the valve body as the spool moves axially. The lands have sharp edges at the corners thereof at which the flow is controlled in conjunction with the inner ends of the openings in the valve body.
Other objects and advantages will become apparent from the following description taken in conjunction with the drawings.